Folded camera lens designs

ABSTRACT

Digital cameras, optical lens modules for such digital cameras and methods for assembling lens elements in such lens modules. In various embodiments, the digital cameras comprise an optical lens module including N≥3 lens elements L i , each lens element comprising a respective front surface S 2i-1  and a respective rear surface S 2i . In various embodiments the first lens element toward the object side, L 1  and its respective front surfaces S 1  have optical and/or mechanical properties, such as a clear aperture, a clear height and a mechanical height that are larger than respective properties of following lens elements and surfaces. This is done to achieve a camera with large aperture stop, given a lens and/or camera height.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/077,477, which was a 371 application frominternational patent application No. PCT/IB2018/050988 filed Feb. 18,2018 and claims the benefit of U.S. Provisional patent applications No.62/462,438 filed Feb. 23, 2017, 62/478,783 filed Mar. 30, 2017, and62/483,422 filed Apr. 9, 2017, all of which are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The presently disclosed subject matter is generally related to the fieldof digital cameras.

BACKGROUND

Dual-aperture zoom cameras (also referred to as dual-cameras), in whichone camera (also referred to as “sub-camera”) has a Wide FOV (“Widesub-camera”) and the other has a narrow FOV (“Tele sub-camera”), areknown.

International patent publication WO 2016/024192, which is incorporatedherein by reference in its entirety, discloses a “folded camera module”(also referred to simply as “folded camera”) that reduces the height ofa compact camera. In the folded camera, an optical path folding element(referred to hereinafter as “OPFE”) e.g. a prism or a mirror (otherwisereferred to herein collectively as “reflecting element”) is added inorder to tilt the light propagation direction from perpendicular to thesmart-phone back surface to parallel to the smart-phone back surface. Ifthe folded camera is part of a dual-aperture camera, this provides afolded optical path through one lens assembly (e.g. a Tele lens). Such acamera is referred to herein as “folded-lens dual-aperture camera”. Ingeneral, the folded camera may be included in a multi-aperture camera,for example together with two “non-folded” (upright) camera modules in atriple-aperture camera.

SUMMARY

A small height of a folded camera is important to allow a host device(e.g. a smartphone, tablets, laptops or smart TV) that includes it to beas thin as possible. The height of the camera is often limited by theindustrial design. In contrast, increasing the optical aperture of thelens results in an increase in the amount of light arriving at thesensor and improves the optical properties of the camera.

Therefore, there is a need for, and it would be advantageous to have afolded camera in which the height of the lens optical aperture ismaximal for a given camera height and/or for a lens module height.

According to some aspects of the presently disclosed subject matter,there are provided digital cameras comprising an optical lens moduleincluding N≥3 lens elements L_(i) having a first optical axis, each lenselement comprising a respective front surface S_(2i-1) and a respectiverear surface S_(2i), the lens element surfaces marked S_(k) where1≤k≤2N, an image sensor, and a reflecting element, inclined with respectto the first optical axis so as to provide a folded optical path betweenan object and the lens elements, wherein each lens element surface has aclear height value CH(S_(k)) and wherein a clear height value CH(S₁) ofsurface S₁ is greater than a clear height value of each of surfaces S₂to S_(2N).

In an exemplary embodiment, the N lens elements have an axial symmetry.

In an exemplary embodiment, CH(S₁)≥1.1×CH(S₂).

In an exemplary embodiment, CH(S₁)≥1.2×CH(S_(k)) for 3≤k≤2N.

In an exemplary embodiment, the digital camera has a total track lengthTTL and a focal back length BFL and wherein BFL≥0.3×TTL.

In an exemplary embodiment, L₁ is made of glass.

In an exemplary embodiment, L₁ is made of plastic.

In an exemplary embodiment, L_(i) is made of plastic for any 2≤i≤N.

In an exemplary embodiment, the optical lens module is a front aperturelens module.

In an exemplary embodiment, CH(S₁)<7 mm.

In some exemplary embodiments, each respective lens element surfaceS_(k) has a clear aperture value CA(S_(k)). In an exemplary embodiment,clear aperture value CA(S₁) of surface S₁ is greater than a clearaperture value of each of surfaces S₂ to S_(2N). In an exemplaryembodiment, CA(S₁) is equal to clear aperture value CA(S_(2N)), andCA(S₁) is greater than CA(S_(k)) for 2≤k≤2N−1.

In an exemplary embodiment, CA(S₁) is substantially equal to CH(S₁).

In an exemplary embodiment, CA(S₁)≥1.1×CA(S₂).

In an exemplary embodiment, CA(S₁)≥1.2×CH(S_(k)) for 3≤k≤2N.

1. In an exemplary embodiment, at least some of the lens elements have awidth W_(L) greater than their height H_(L)

In some exemplary embodiments, the optical lens module includes a cavitythat holds the plurality of lens elements, wherein the cavity comprisesa first portion in which the first lens element L₁ is located and asecond portion in which a least one of the other lens elements arelocated, wherein the height of the first portion is greater than theheight of the second portion.

In some exemplary embodiments, the optical lens module includes a cavitythat holds at least some of lens elements L₂ to L_(N), wherein firstlens element L₁ is located outside of the optical lens module.

In some exemplary embodiments, the image sensor is a rectangular sensoror a circular sensor.

In some exemplary embodiments, N≤6.

According to an aspect of the presently disclosed subject matter, thereis provided a digital dual-camera comprising a camera of any of theembodiment mentioned above, wherein the camera is a Tele sub-cameraconfigured to provide a Tele image, and a Wide sub-camera configured toprovide a Wide image.

According to some aspects of the presently disclosed subject matter,there is provided a digital camera comprising an optical lens moduleincluding N≥3 lens elements L_(i) having a first optical axis, each lenselement comprising a respective front surface S_(2i−1) and a respectiverear surface S_(2i), the lens element surfaces marked S_(k) where1≤k≤2N, an image sensor, and a reflecting element inclined with respectto the first optical axis so as to provide a folded optical path betweenan object and the lens elements, wherein each lens element surface has aclear aperture value CA(S_(k)) and wherein clear aperture value CA(S₁)is greater than CA(S_(k)) for 2≤k≤2N.

In an exemplary embodiment, CA(S₁)≥1.1×CA(S₂).

In an exemplary embodiment, CA(S₁)≥1.2×CH(S_(k)), for 3≤k≤2N.

In some exemplary embodiments, the optical lens module includes a cavitythat holds the plurality of lens elements, wherein a height of cavity,measured along an axis orthogonal to the first optical axis, is variablealong the first optical axis.

In some exemplary embodiments, the cavity comprises a first portion inwhich the first lens element L₁ is located and a second portion at whichat least one of the other lens elements is located, and wherein theheight of the first portion of the cavity is greater than the height ofthe second portion of the cavity.

In some exemplary embodiments, the optical lens module further comprisesa lens barrel (or simply “barrel”) with a cavity in which at least someof lens elements L₂ to L_(N) are held and wherein lens element L₁ islocated outside of the barrel.

According to another aspect of the presently disclosed subject matter, acamera described above is a Tele sub-camera configured to provide a Teleimage and is included together with a Wide sub-camera configured toprovide a Wide image in a dual-camera.

According to another aspect of the presently disclosed subject matter,there is provided a digital camera comprising N lens elements having asymmetry along a first optical axis, wherein N is equal to or greaterthan 3, an image sensor, a reflecting element operative to provide afolded optical path between an object and the image sensor, and a barrelwith a cavity in which the plurality of lens elements are held, whereina height of cavity, measured along an axis orthogonal to the firstoptical axis, is variable along the first optical axis, wherein thecavity comprises a first portion in which the first lens element L₁ islocated and a second portion at which at least one of the other lenselements is located, and wherein the height of the first portion of thecavity H₁ is greater than the height of the second portion of the cavityH₂, so that H₁>1.1×H₂.

According to another aspect of the presently disclosed subject matter,there is provided a digital camera comprising N lens elements L₁ toL_(N) having axial symmetry along a first optical axis, wherein N isequal to or greater than 3, an image sensor, a reflecting elementoperative to provide a folded optical path between an object and theimage sensor, and a barrel with a cavity in which at least some of thelens elements L₂ to L_(N) are held, and wherein the lens element L₁ islocated outside of barrel.

In an exemplary embodiment, L_(N) is located outside the barrel.

According to some aspects of the presently disclosed subject matter,there is provided an optical lens module comprising a barrel having acavity surrounded by walls and N lens elements L₁ to L_(N), wherein N isequal to or greater than 3, wherein L₁ has a portion which is notcompletely surrounded by the cavity and wherein walls of the cavity arealigning a center of lens element L₁ with the first optical axis.

In an exemplary embodiment, L_(N) has a portion which is not completelysurrounded by the cavity and wherein walls of the cavity are aligning acenter of lens element L_(N) with the first optical axis.

In an exemplary embodiment, at least one of an extremity of the wallsand an extremity of lens element L₁ is shaped so that the extremity ofthe walls acts a stop for at least a portion of lens element L₁, therebysubstantially aligning a center of lens element L₁ with the firstoptical axis.

In an exemplary embodiment, a first portion of lens element L₁ islocated in the cavity between the extremity of the walls and a secondportion of lens element L₁ is located outside the barrel and wherein athickness of the second portion of lens element L₁ along the firstoptical axis is greater than a thickness of the first portion of lenselement L₁ along the first optical axis.

In an exemplary embodiment, a cross-section of the extremity of thewalls has a stepped shape.

In an exemplary embodiment, a cross-section of the extremity of lenselement L₁ has a stepped shape.

In an exemplary embodiment, a cross-section of the extremity of thewalls has a sloping shape.

In an exemplary embodiment, the extremity of the walls comprises achamfer.

In an exemplary embodiment, the lens module further comprises a coverfor protecting the lens, the cover covering lens element L₁.

In an exemplary embodiment, the cover has an extreme point beyond lenselement L₁.

In an exemplary embodiment, the cover blocks light from entering amechanical part of lens element L₁.

According to some aspects of the presently disclosed subject matter,there is provided an optical lens module comprising a plurality N≥3 oflens elements L_(i) wherein 1≤i≤N, each lens element comprising arespective front surface S_(2i−1) and a respective rear surface S_(2i),the lens element surfaces marked S_(k) where 1≤k≤2N, wherein each lenselement surface has a clear aperture value CA(S_(k)), wherein CA(S₁) issubstantially equal to CA(S_(2N)) and wherein CA(S₁) is greaterCA(S_(k)) for 2≤k≤2N−1.

According to some aspects of the presently disclosed subject matter,there is provided an optical lens module comprising a plurality N≥3 oflens elements L, wherein 1≤i≤N, each lens element comprising arespective front surface S_(2i−1) and a respective rear surface S_(2i),the lens element surfaces marked S_(k) where 1≤k≤2N, wherein each lenselement surface has a clear aperture value CA(S_(k)) and wherein CA(S₁)is greater CA(S_(k)) for 2≤k≤2N.

According to some aspects of the presently disclosed subject matter,there is provided a digital camera comprising an image sensor, areflecting element operative to provide a folded optical path between anobject and the image sensor, and an optical lens module as describedabove.

According to another aspect of the presently disclosed subject matter,there is provided an optical lens module comprising a barrel having abarrel height H and N lens elements L₁ to L_(N), wherein N is equal toor greater than 3 and wherein a height H_(L1) of lens element L₁satisfies or fulfills H_(L1)≥H. In an exemplary embodiment, H_(LN)≥H. Inan exemplary embodiment, H_(LN)=H_(L1).

According to another aspect of the presently disclosed subject matter,there is provided an optical lens module comprising N lens elements L₁to L_(N), wherein N≥3, wherein each lens element L_(i) has a heightH_(Li) for 1≤i≤N and wherein H_(L1)≥H_(LN)>H_(L2).

In an exemplary embodiment, H_(L1)>H_(Li) for 3≤i≤N−1.

According to another aspect of the presently disclosed subject matter,there is provided a method for assembling an optical lens module,comprising: inserting a first lens element L₁ of N lens elements into abarrel from an object side of the barrel, fixedly attaching lens elementL₁ to the barrel, inserting other lens elements L₂ to L_(N) and spacersR₁ to R_(N) that separate respective lens elements from an image side ofthe barrel in an insertion order R₁, L₂ . . . R_(N−1), L_(N), andfixedly attaching lens element L_(N) to the lens module.

According to another aspect of the presently disclosed subject matter,there is provided a mobile electronic device comprising an internaldigital camera integrated inside a housing of the mobile electronicdevice, wherein the digital camera is in accordance with any one of theaspects mentioned above, or comprises any of the optical lens moduledescribed above.

According to another aspect of the presently disclosed subject matterthere is provided a multiple-aperture camera comprising at least oneWide sub-camera and at least one Tele sub-camera, which is in accordancewith any one of the aspects mentioned above, or comprises any of theoptical lens module described above.

According to another aspect of the presently disclosed subject matter,the reflecting element is a rotating reflecting element capable of beingrotated around one or two axes in order to move the position of a fieldof view (FOV) of the digital camera and capture a plurality of adjacentnon-overlapping or partially overlapping images at a plurality ofrespective positions, and the digital camera is configured to generatefrom the plurality of images a composite image having an overall imageFOV greater than an FOV of the digital camera.

In some exemplary embodiment, the digital camera according to the aboveaspect further comprises an actuator configured to apply rotationalmovement around one or two axes to the rotating reflecting element, theactuator operatively connected to a controller configured to control theactuator to cause the camera to scan an area corresponding to arequested zoom factor, the area being greater than the FOV of thedigital camera, and to capture the plurality of images where each imageis captured at a different position in the scanned area.

In an exemplary embodiment, the size of the composite image is generatedby the stitching of 4 Tele images.

In an exemplary embodiment, the size of the composite image is generatedby the stitching of 6 Tele images.

In an exemplary embodiment, the size of the composite image is generatedby the stitching of 9 Tele images.

In an exemplary embodiment, a combined size of the plurality of image isgreater than the size of the composite image.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples of embodiments disclosed herein are describedbelow with reference to figures attached hereto that are listedfollowing this paragraph. The drawings and descriptions are meant toilluminate and clarify embodiments disclosed herein, and should not beconsidered limiting in any way. Like elements in different drawings maybe indicated by like numerals. Elements in the drawings are notnecessarily drawn to scale. In the drawings:

FIG. 1A is a general isometric view of an example of a known foldedcamera;

FIG. 1B is a side view of the camera of FIG. 1A;

FIG. 1C is a general isometric view of an example of a known cameracomprising a folded Tele sub-camera and a Wide sub-camera;

FIG. 1D is a side view of the camera of FIG. 1C;

FIG. 2A is a schematic view of one embodiment of lens elements withlight rays according to some examples of the presently disclosed subjectmatter;

FIG. 2B is another schematic view of the lens elements of FIG. 2A;

FIG. 3A is a schematic view of impact points of optical rays impinging aconvex surface of a lens element, and a schematic view of the orthogonalprojection of the impact points on a plane P, according to some examplesof the presently disclosed subject matter;

FIG. 3B is a schematic view of impact points of optical rays impinging aconcave surface of a lens element, and a schematic view of theorthogonal projection of the impact points on a plane P, according tosome examples of the presently disclosed subject matter;

FIG. 4 is a schematic representation of the orthogonal projection of theimpact points on a plane P, and of a clear height value (“CH”),according to some examples of the presently disclosed subject matter;

FIG. 5 is a schematic representation of the orthogonal projection of theimpact points on a plane P, and of a clear aperture value (“CA”),according to some examples of the presently disclosed subject matter;

FIG. 6 is a schematic representation of a side view of an optical lensmodule for holding the lens elements, according to some examples of thepresently disclosed subject matter;

FIG. 7 is a schematic representation of a side view of an optical lensmodule for holding the lens elements, according to other examples of thepresently disclosed subject matter;

FIG. 8 is a schematic representation of an example of an optical lensmodule comprising a plurality of lens elements, according to thepresently disclosed subject matter;

FIG. 9A is a schematic representation of another example of an opticallens module comprising a plurality of lens elements, according to thepresently disclosed subject matter;

FIG. 9B depicts a variant of the example of FIG. 9A;

FIG. 10 is a schematic representation of another example of an opticallens module comprising a plurality of lens elements, according to thepresently disclosed subject matter;

FIG. 11A is a schematic representation of an isometric view of a barreland of a plurality of lens elements before their insertion into thebarrel, according to the presently disclosed subject matter;

FIG. 11B depicts a cross-section view of the example of FIG. 11A, alongplane Y-Z;

FIG. 11C depicts a cross-section view of the example of FIG. 11A, alongplane X-Z;

FIG. 11D depicts a front view of the example of FIG. 11A;

FIG. 11E depicts another isometric view of the example of FIG. 11A afterthe insertion of the lens elements in the barrel;

FIG. 11F is a schematic representation of a front view of a lenselement;

FIG. 12 is a schematic representation of a manufacturing process of theoptical lens module of FIGS. 11A to FIG. 11E.

FIG. 13A is a schematic representation of an isometric view of aplurality of lens elements;

FIGS. 13B is a schematic representation of an isometric view of anoptical lens module comprising the plurality of lens elements of FIG.13A and a barrel;

FIGS. 13C is yet another schematic representation of an isometric viewof an optical lens module comprising the plurality of lens elements ofFIG. 13A and a barrel.

FIG. 14 is a schematic illustration of a stitched image generated bycapturing and stitching together 4 Tele images, according to someexamples of the presently disclosed subject matter;

FIG. 15 is a schematic illustration of a stitched image generated bycapturing and stitching together 6 Tele images, according to someexamples of the presently disclosed subject matter;

FIG. 16 is a schematic illustration of a stitched image generated bycapturing and stitching together 9 Tele images, according to someexamples of the presently disclosed subject matter;

FIG. 17A shows an isometric view of another embodiment of a barrel withlens elements, according to the presently disclosed subject matter;

FIG. 17B shows a side cut of the barrel and lens elements of FIG. 17A;

FIG. 17C shows an exploded view of the lens elements of FIG. 17B;

FIG. 17D shows a side cut of another barrel with lens elements,according to the presently disclosed subject matter;

FIG. 18A shows an isometric view of yet another embodiment of a lensmodule with a barrel and lens elements, according to the presentlydisclosed subject matter;

FIG. 18B shows a side cut of the lens module of FIG. 18A;

FIG. 18C shows an exploded view of the lens module of FIG. 18B;

FIG. 19A shows a side cut of yet another embodiment of a lens modulewith a barrel and lens elements, according to the presently disclosedsubject matter;

FIG. 19B shows the lens module of FIG. 19A in an exploded view;

FIG. 20 shows a side cut of yet another embodiment of a barrel with lenselements, according to the presently disclosed subject matter;

FIG. 21A is a schematic view of another embodiment of lens elementsshowing light rays, according to another example of the presentlydisclosed subject matter;

FIG. 21B is another schematic view of the lens elements of FIG. 21A;

FIG. 22 is a schematic representation of a side view of optical lensmodule for holding the lens elements of FIGS. 21A, 21B;

FIG. 23 is a schematic representation of a side view of another opticallens module for holding the lens elements of FIGS. 21A, 21B;

FIG. 24 is a schematic representation of yet another example of anoptical lens module comprising a plurality of lens elements, accordingto the presently disclosed subject matter;

FIG. 25A is a schematic representation of an isometric view of anotheroptical lens module, according to the presently disclosed subjectmatter;

FIG. 25B depicts a cross-section view of the lens module of FIG. 25A,along plane Y-Z;

FIG. 25C depicts a cross-section view of the lens module of FIG. 25A,along plane X-Z;

FIG. 25D depicts another isometric view of the lens module of FIG. 25Aafter the insertion of the lens elements into the barrel;

FIG. 26A shows an isometric view of yet another embodiment of a lensmodule with a barrel and lens elements, according to the presentlydisclosed subject matter;

FIG. 26B shows a side cut of lens module of FIG. 26A;

FIG. 26C shows an exploded view of the lens module of FIG. 26B;

FIG. 27 shows an isometric view of yet another embodiment of a lensmodule, according to the presently disclosed subject matter;

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding. However, it will beunderstood by those skilled in the art that the presently disclosedsubject matter may be practiced without these specific details. In otherinstances, well-known methods have not been described in detail so asnot to obscure the presently disclosed subject matter.

It is appreciated that certain features of the presently disclosedsubject matter, which are, for clarity, described in the context ofseparate embodiments, may also be provided in combination in a singleembodiment. Conversely, various features of the presently disclosedsubject matter, which are, for brevity, described in the context of asingle embodiment, may also be provided separately or in any suitablesub-combination.

The term “processing unit” as disclosed herein should be broadlyconstrued to include any kind of electronic device with data processingcircuitry, which includes for example a computer processing deviceoperatively connected to a computer memory (e.g. digital signalprocessor (DSP), a microcontroller, a field programmable gate array(FPGA), an application specific integrated circuit (ASIC), etc.) capableof executing various data processing operations.

Furthermore, for the sake of clarity the term “substantially” is usedherein to imply the possibility of variations in values within anacceptable range. According to one example, the term “substantially”used herein should be interpreted to imply possible variation of up to10% over or under any specified value. According to another example, theterm “substantially” used herein should be interpreted to imply possiblevariation of up to 5% over or under any specified value. According to afurther example, the term “substantially” used herein should beinterpreted to imply possible variation of up to 2.5% over or under anyspecified value.

FIGS. 1A and 1B illustrate a known digital folded camera 100, which mayoperate for example as a Tele camera. Digital camera 100 comprises afirst reflecting element (e.g. mirror or prism, and also referred tosometimes as “optical path folding element” (OPFE)) 101, a plurality oflens elements (not visible in this representation, but visible e.g. inFIGS. 2A and 2B) and an image sensor 104. The lens elements (and alsobarrel, the optical lens module) may have axial symmetric along a firstoptical axis 103. At least some of the lens elements can be held by astructure called a “barrel” 102. An optical lens module comprises thelens elements and the barrel. The barrel can have a longitudinalsymmetry along optical axis 103. In FIGS. 1A to 1D, the cross-section ofthis barrel is circular. This is however not mandatory and other shapescan be used.

The path of the optical rays from an object (not shown) to image sensor104 defines an optical path (see optical paths 105 and 106, whichrepresent portions of the optical path).

OPFE 101 may be a prism or a mirror. As shown in FIG. 1A, OPFE 101 canbe a mirror inclined with respect to optical axis 103. In other cases(not shown, see for example PCT/IB2017/052383), OPFE 101 can be a prismwith a back surface inclined with respect to optical axis 103. OPFEfolds the optical path from a first optical path 105 to a second opticalpath 106. Optical path 106 is substantially parallel to the optical axis103. The optical path is thus referred to as “folded optical path”(indicated by optical paths 105 and 106) and camera 100 is referred toas “folded camera”. The lens module comprises the plurality of lenselements.

In particular, in some examples, OPFE 101 can be inclined atsubstantially 45° with respect to optical axis 103. In FIG. 1A, OPFE 101is also inclined at substantially 45° with respect to optical path 105.

In some known examples, image sensor 104 lies in a X-Y planesubstantially perpendicular to optical axis 103. This is however notlimiting and the image sensor 104 can have a different orientation. Forexample, and as described in WO 2016/024192, image sensor 104 can be inthe XZ plane. In this case, an additional OPFE can be used to reflectthe optical rays towards image sensor 104.

According to some examples, image sensor 104 has a rectangular shape.According to some examples, image sensor 104 has a circular shape. Theseexamples are however not limiting.

In various examples camera 100 may be mounted on a substrate 109, e.g. aprinted circuit board (PCB), as known in the art.

Two sub-cameras, for example a regular Wide sub-camera 130 and a Telesub-camera 100 may be included in a digital camera 170 (also referred toas dual-camera or dual-aperture camera). A possible configuration isdescribed with reference to FIGS. 1C and 1D. In this example, Telesub-camera 100 is according to the camera described with reference toFIGS. 1A and 1B. The components of Tele sub-camera 100 thus have thesame reference numbers as in FIGS. 1A and 1B, and are not describedagain.

Wide camera 130 can include an aperture 132 (indicating object side ofthe camera) and an optical lens module 133 (or “Wide lens module” inshort) with a symmetry (and optical) axis 134 in the Y direction, aswell as a Wide image sensor 135. The Wide sub-camera comprises a Widelens module configured to provide a Wide image, wherein the Widesub-camera has a Wide field of view (FOV_(W)) and the Tele sub-camerahas a Tele field of view (FOV_(T)) narrower than FOV_(W). Notably, inother examples a plurality of Wide sub-cameras and/or a plurality ofTele sub-cameras can be incorporated and operative in a single digitalcamera.

According to one example, the Wide image sensor 135 lies in the X-Zplane, while image sensor 104 (which is in this example is a Tele imagesensor) lies in a X-Y plane substantially perpendicular to optical axis103.

In the examples of FIGS. 1A to 1D, camera 100 can further include (or beotherwise operatively connected to) a processing unit comprising one ormore suitably configured processors (not shown) for performing variousprocessing operations, for example processing the Tele image and theWide image into a fused output image.

The processing unit may include hardware (HW) and software (SW)specifically dedicated for operating with the digital camera.Alternatively, a processor of an electronic device (e.g. its native CPU)in which the camera is installed can be adapted for executing variousprocessing operations related to the digital camera (including, but notlimited to, processing the Tele image and the Wide image into an outputimage).

Attention is now drawn to FIGS. 2A and 2B, which show schematic view ofa lens module 200 having lens elements shown with optical rays accordingto some examples of the presently disclosed subject matter. Lens module200 is shown without a lens barrel. FIG. 2A shows optical ray tracing oflens module 200 while FIG. 2B shows only the lens elements for moreclarity. In addition, both figures show an image sensor 202 and anoptical element 205.

Lens module 200 includes a plurality of N lens elements L_(i) (wherein“i” is an integer between 1 and N). L₁ is the lens element closest tothe object side and L_(N) is the lens element closest to the image side,i.e. the side where the image sensor is located. This order holds forall lenses and lens elements disclosed herein. Lens elements L_(i) canbe used e.g. as lens elements of camera 100 represented in FIGS. 1A and1B or as lens elements of the Tele sub-camera 100 of FIGS. 1C and 1D. Asshown, the N lens elements are axial symmetric along optical axis 103.

In the examples of FIGS. 2A and 2B, N is equal to four. This is howevernot limiting and a different number of lens elements can be used.According to some examples, N is equal to or greater than 3 For example,N can be equal to 3, 4, 5, 6 or 7.

In the examples of FIGS. 2A and 2B, some of the surfaces of the lenselements are represented as convex, and some are represented as concave.The representation of FIGS. 2A and 2B is however not limiting and adifferent combination of convex and/or concave surfaces can be used,depending on various factors such as the application, the desiredoptical power, etc.

Optical rays (after their reflection by a reflecting element, such asOPFE 101) pass through lens elements L_(i) and form an image on an imagesensor 202. In the examples of FIGS. 2A and 2B, the optical rays passthrough an optical element 205 (which comprises a front surface 205 aand a rear surface 205 b, and can be e.g. a cut-off filter) beforeimpinging on image sensor 202. This is however not limiting, and in someexamples, optical element 205 is not present. Optical element 205 may befor example infra-red (IR) filter, and/or a glass image sensor dustcover.

Each lens element L_(i) comprises a respective front surface S_(2i−1)(the index “2i−1” being the number of the front surface) and arespective rear surface S_(2i) (the index “2i” being the number of therear surface), where “i” is an integer between 1 and N. This numberingconvention is used throughout the description. Alternatively, as donethroughout this description, lens surfaces are marked as “S_(k)”, with krunning from 1 to 2N. The front surface and the rear surface can be insome cases aspherical. This is however not limiting.

As used herein the term “front surface” of each lens element refers tothe surface of a lens element located closer to the entrance of thecamera (camera object side) and the term “rear surface” refers to thesurface of a lens element located closer to the image sensor (cameraimage side).

As explained below, a clear height value CH(S_(k)) can be defined foreach surface S_(k) for 1≤k≤2N), and a clear aperture value CA(S_(k)) canbe defined for each surface S_(k) for 1≤k≤2N). CA(S_(k)) and CH(S_(k))define optical properties of each surface S_(k) of each lens element.

In addition, and as shown e.g. in FIG. 6, a height (“H_(Li)”, for 1≤i≤N)is defined for each lens element L_(i). H_(i) corresponds, for each lenselement L_(i), to the maximal height of lens element L_(i) measuredalong an axis perpendicular to the optical axis of the lens elements (inthe example in FIG. 6, H_(Li) is measured along optical path 105 whichis perpendicular to optical axis 103). For a given lens element, theheight is greater than, or equal to the clear height value CH and theclear aperture value CA of the front and rear surfaces of this givenlens element. Typically, for an axial symmetric lens element, H_(Li) isthe diameter of lens element L_(i) as seen in FIG. 11F. Typically, foran axial symmetric lens element, H_(Li)=max{CA(S_(2i−1)),CA(S_(2i))}+mechanical part size. The mechanical part and its propertiesare defined below (FIGS. 11E, 11F and 17A-D). The mechanical part sizecontribution to H_(Li) is typically 200 μm-1000 μm.

In addition, as also shown in FIG. 6, a height H is defined for the lensbarrel. For any axis A which is perpendicular to the optical axis of alens module, a diameter D_(A) is defined as the maximal distancemeasured along axis A of the lens module. H is defined as the minimum ofall D_(A)s for all possible axes A. In the example in FIG. 6, Hcorresponds to the maximal height of the barrel measured along an axisperpendicular to the optical axis 103 of the lens module and parallel tooptical path 105.

In addition, as also shown in FIG. 7, a height H_(C) is defined for thecavity of a lens barrel. H_(C) corresponds to the height of the cavitybarrel measured along an axis perpendicular to the optical axis of thelens module (in the example in FIG. 7, H_(C) is measured along opticalpath 105 which is perpendicular to optical axis 103). In some examples,where the cavity barrel is axial-symmetric, H_(C) is the internaldiameter of the cavity barrel.

According to some examples of the presently disclosed subject matter,the closest lens element to the object side (L₁) has a height which isgreater than the height of each of the other lens elements. Anon-limiting example is shown in FIG. 6, where H_(L1) is greater thanH_(L2), H_(L3) and H_(L4).

According to some examples of the presently disclosed subject matter,the closest lens element to the object side (L₁) and the closest lenselement to the image sensor (L_(N)) have a height which is substantiallyequal and is greater than the height of each of the other lens elements.A non-limiting example is shown in FIG. 21B, where H_(L1) equal toH_(L5) and are greater than H_(L2), H_(L3) and H_(L4).

As shown in FIGS. 3A, 3B and 4, each optical ray that passes through asurface S_(k) (for 1≤k≤2N) impinges this surface on an impact point IP.Optical rays enter lens module 200 from surface S₁, and pass throughsurfaces S₂ to S_(2N) consecutively. Some optical rays can impinge onany surface S_(k) but cannot/will not reach image sensor 202. For agiven surface S_(k), only optical rays that can form an image on imagesensor 202 are considered forming a plurality of impact points IP areobtained. CH(S_(k)) is defined as the distance between two closestpossible parallel lines (see lines 400 and 401 in FIG. 4 located on aplane P orthogonal to the optical axis of the lens elements (in therepresentation of FIGS. 3A and 3B, plane P is parallel to plane X-Y andis orthogonal to optical axis 103), such that the orthogonal projectionIP_(orth) of all impact points IP on plane P is located between the twoparallel lines. CH(S_(k)) can be defined for each surface S_(k) (frontand rear surfaces, with 1≤k≤2N).

The definition of CH(S_(k)) does not depend on the object currentlyimaged, since it refers to the optical rays that “can” form an image onthe image sensor. Thus, even if the currently imaged object is locatedin a black background which does not produce light, the definition doesnot refer to this black background since it refers to any optical raysthat “can” reach the image sensor to form an image (for example opticalrays emitted by a background which would emit light, contrary to a blackbackground).

For example, FIG. 3A illustrates the orthogonal projections IP_(orth,1),IP_(orth,2) of two impact points IP₁ and IP₂ on plane P which isorthogonal to optical axis 103. By way of example, in the representationof FIG. 3A, surface S_(k) is convex.

FIG. 3B illustrates the orthogonal projections IP_(orth,3), IP_(orth,4)of two impact points IP₃ and IP₄ on plane P. By way of example, in therepresentation of FIG. 3B, surface S_(k) is concave.

In FIG. 4, the orthogonal projection IP_(orth) of all impact points IPof a surface S_(k) on plane P is located between parallel lines 400 and401. CH(S_(k)) is thus the distance between lines 400 and 401.

Attention is drawn to FIG. 5. According to the presently disclosedsubject matter, a clear aperture CA(S_(k)) is defined for each givensurface S_(k) (for 1≤k≤2N), as the diameter of a circle, wherein thecircle is the smallest possible circle located in a plane P orthogonalto the optical axis 103 and encircling all orthogonal projectionsIP_(orth) of all impact points on plane P. As mentioned above withrespect to CH(S_(k)), it is noted that the definition of CA(S_(k)) alsodoes not depend on the object which is currently imaged.

As shown in FIG. 5, the circumscribed orthogonal projection IP_(orth) ofall impact points IP on plane P is circle 500. The diameter of thiscircle 500 defines CA(S_(k)).

Detailed optical data and surface data are given in Tables 1-2 for theexample of the lens elements in FIG. 2A-2B, in Tables 3 and 4 for theexample of the lens elements in FIGS. 6-9, in Tables 5 and 6 for theexample of the lens elements in FIG. 20 and in Tables 7 and 8 for theexample of the lens elements in FIG. 21A-21B (see below). The valuesprovided for these examples are purely illustrative and according toother examples, other values can be used.

In the tables below, the units of the radius of curvature (“R”), thelens element thickness (“Thickness”) and the clear aperture (“CA”) areexpressed in millimeters.

Line “0” of Tables 1, 3 and 5 and 7 describes parameters associated tothe object (not visible in the figures); the object is being placed at 1km from the system, considered to be an infinite distance.

Lines “1” to “8” of Tables 1 to 4 describe respectively parametersassociated to surfaces S₁ to S₈. Lines “1” to “10” of Tables 5 to 8describe respectively parameters associated with surfaces S₁ to S₁₀.

Lines “9”, “10” and “11” of Tables 1 and 3, and lines “11”, “12” and“13” in Tables 5 and 7 describe respectively parameters associated tosurfaces 205 a, 205 b of optical element 205 and of a surface 202 a ofthe image sensor 202.

In lines “i” of Tables 1, 3 and 5 (with i between 1 and 10 in tables 1and 3 and i between 1 and 12 in Table 5), the thickness corresponds tothe distance between surface S_(i) and surface S_(i+1), measured alongthe optical axis 103 (which coincides with the Z axis).

In line “11” of Tables 1, 3 (line “13” in Tables 5 and 7), the thicknessis equal to zero, since this corresponds to the last surface 202 a.

“BK7”, “K26R”, “EP6000” and “H-ZK3” are conventional materials which areknown to a person skilled in the art and which are mentioned by way ofexample.

“BK7” is characterized by the approximate following parameters:

-   -   Refractive index of 1.5168, and    -   Abbe number of 64.16733.    -   “K26R” is a material manufactured by Zeon Corporation, and is        characterized by the approximate following parameters:    -   Refractive index of 1.534809, and    -   Abbe number of 55.663857.

“EP6000” is a material manufactured by Mitsubishi, and is characterizedby the approximate following parameters:

-   -   Refractive index of 1.6397, and    -   Abbe number of 23.5288.

“H-ZK3” is a type of glass characterized by the approximate followingparameters:

-   -   Refractive index of 1.5891, and    -   Abbe number of 61.25.        In Table 7, the properties of each surface material are given,        with “Nd” as refractive index and “Vd” as Abbe number.

The equation of the surface profiles of each surface S_(k) (for kbetween 1 and 2N) is expressed by:

$z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {A_{1}r^{4}} + {A_{2}r^{6}} + {A_{3}r^{8}} + {A_{4}r^{10}} + {A_{5}r^{12}} + {A_{6}r^{14}} + {A_{7}r^{16}}}$

where “z” is the position of the profile of the surface S_(k) measuredalong optical axis 103 (coinciding with the Z axis, wherein z=0corresponds to the intersection of the profile of the surface S_(k) withthe Z axis), “r” is the distance from optical axis 103 (measured alongan axis which is perpendicular to optical axis 103), “K” is the coniccoefficient, c=1/R where R is the radius of curvature, and A_(n) (n from1 to 7) are coefficients given in Tables 2 and 4 for each surface S_(k).The maximum value of r, “max r”, is equal to D/2.

In the example of FIGS. 2A and 2B, the following optical properties areachieved:

-   -   TTL=13.6 mm    -   BFL=4.93 mm    -   EFL (effective focal length)=13.8 mm    -   CA(S₁)=CH(S₁)=5 mm    -   CA(S₂)=CH(S₂)=4.4 mm    -   For k between 3 and 8, CA(S_(k))≤3.8 mm, CH(S_(k))≤CA(S_(k)).    -   f/#=2.76    -   Focal length of L₁: f₁=5.57 mm, f₁/EFL=0.4    -   Sensor diagonal (SD) 5.86 mm, last surface clear aperture        CA(S_(2N))=3.8 mm, CA(S_(2N))/SDL=0.65.

In the example of FIG. 6, the following optical properties are achieved:

-   -   TTL=11.1 mm,    -   BFL=4.3 mm,    -   EFL (effective focal length)=11.2 mm,    -   CA(S₁)=CH(S₁)=4.32 mm,    -   CA(S₂)=CH(S₂)=3.52 mm, and    -   For k between 3 and 8, CA(S_(k))≤3.2 mm, CH(S_(k))≤CA(S_(k))).    -   f/#=2.5    -   Focal length of L₁: f₁=4.54 mm, f₁/EFL=0.4    -   Sensor diagonal (SD) 5.24 mm, last surface clear aperture        CA(S_(2N))=3.2 mm, CA(S_(2N))/SDL=0.61.

In the example of FIG. 20, the following optical properties areachieved:

-   -   TTL=15 mm    -   BFL=6.9 mm    -   EFL=16 mm    -   CA(S₁)=CH(S₁)=5.92 mm    -   CA(S₂)=CH(S₂)=5.1 mm    -   For k between 3 and 10, CA(S_(k))≤4.0 mm, CH(S_(k))≤CA(S_(k)).    -   f/#=2.7    -   Focal length of L₁: f₁=8.1 mm, f_(1/)EFL=0.506    -   Sensor diagonal (SD) mm, last surface clear aperture        CA(S_(2N))=3.52 mm, CA(S_(2N))/SDL=0.6

In the example of FIGS. 21A and 21B, the following optical propertiesare achieved:

-   -   TTL=7.78 mm    -   BFL=3.23 mm    -   EFL (effective focal length)=7.97 mm    -   CA(S₁)=CH(S₁)=3.6 mm    -   CA(S₂)=CH(S₂)=3.45 mm    -   For k between 3 and 8, CA(S_(k))≤3.4 mm, CH(S_(k))≤CA(S_(k)).    -   CA(S2N−1)=3.36 mm, CH(S2N−1)=2.842 mm    -   CA(S_(2N))=3.6 mm, CH(S_(2N−1))=3.064 mm    -   f/#=2.2    -   Focal length of L₁: f₁=3.972 mm, f₁/EFL=0.498    -   Sensor diagonal (SD) 5.86 mm, CA(S_(2N))/SD=0.615.        In this application and for the properties above, the following        symbols and abbreviations are used, all of which are terms known        in the art:    -   TTL: The “total track length” is defined as the maximal        distance, measured along an axis parallel to the optical axis,        between a point of the front surface S₁ of the first lens        element L₁ and the image sensor, when the system is focused to        an infinity object distance.    -   BFL: The “focal back length” is defined as the minimal distance,        measured along an axis parallel to the first optical axis,        between a point of the rear surface S_(2N) of the last lens        element L_(N) and the image sensor, when the system is focused        to an infinity object distance.    -   EFL: Effective focal length of a lens module (assembly of lens        elements L₁ to L_(N))    -   f/#: f-number, the ratio of the EFL to the aperture stop        diameter.    -   Aperture stop: the opening which limits the amount of light        which passes through an optical system.

TABLE 1 Conic # R Thickness Material CA/2 coefficient K 0 Infinity1.00E+06 1 4.018 3.122 K26R 2.50 −0.918 2 −8.544 0.427 2.20 −13.319 3−11.602 0.383 EP6000 1.90 −68.256 4 4.252 0.668 1.90 0.035 5 12.4103.072 EP6000 1.90 9.316 6 −9.884 0.565 1.90 −50.842 7 −5.080 0.434 K26R1.90 −30.682 8 −57.279 4.429 1.90 −207.271 9 Infinity 0.210 BK7 10Infinity 0.289 11 Infinity 0.000

TABLE 2 # A1 A2 A3 A4 A5 A6 A7 1 1.0982E−03 −5.6900E−05 3.0019E−06−3.0442E−07 −2.0532E−07 2.1748E−08 −2.5134E−09 2 1.4662E−03 −6.8269E−043.6775E−05 1.2874E−07 −1.5311E−06 1.6528E−07 0.0000E+00 3 −4.4641E−032.3303E−03 −6.0231E−04 5.0714E−05 2.4477E−06 −3.4785E−07 −1.2814E−08 4−4.6819E−03 2.7039E−03 −4.9103E−04 −6.1960E−05 4.4187E−05 −5.1739E−060.0000E+00 5 −8.9765E−04 2.5621E−04 −1.2915E−04 −5.1021E−06 9.6811E−06−1.2420E−06 0.0000E+00 6 −2.6288E−03 8.0824E−04 −4.4175E−05 −1.8619E−05−1.2620E−05 4.5041E−06 0.0000E+00 7 −4.3474E−02 8.7969E−03 −7.7260E−04−2.7259E−04 1.8367E−05 9.9215E−06 0.0000E+00 8 −1.9365E−02 1.5956E−033.4614E−04 −1.1796E−04 −1.3790E−05 5.9480E−06 −2.5281E−07

TABLE 3 Conic # R Thickness Material CA/2 coefficient K 0 Infinity1.00E+06 1 3.252 2.571 K26R 2.16 −0.763 2 −7.055 0.253 1.76 −17.097 3−10.672 0.444 EP6000 1.60 −75.529 4 3.302 0.309 1.45 −0.248 5 10.3222.569 EP6000 1.47 15.386 6 −7.343 0.403 1.46 −43.555 7 −4.066 0.282 K26R1.45 −22.400 8 −39.758 3.804 1.60 −20.554 9 Infinity 0.210 BK7 10Infinity 0.290 11 Infinity 0.000

TABLE 4 # A1 A2 A3 A4 A5 A6 A7 1 1.6499E−03 −1.0742E−04 5.7901E−06−8.6098E−08 −1.7012E−06 1.8672E−07 −2.7417E−08 2 3.0173E−03 −1.4633E−037.0329E−05 −1.5844E−05 −3.5031E−06 8.0518E−07 0.0000E+00 3 −6.8586E−035.5011E−03 −1.6856E−03 2.1537E−04 1.2470E−05 −1.0238E−05 9.8851E−07 4−8.1487E−03 5.6510E−03 −7.1159E−04 1.4107E−05 3.5178E−04 1.6510E−050.0000E+00 5 −4.9793E−04 −4.5018E−04 −2.6820E−04 3.0430E−04 2.0799E−041.9782E−05 0.0000E+00 6 −2.4020E−03 1.2967E−03 −2.1528E−04 −1.8139E−04−2.3192E−05 6.9007E−05 0.0000E+00 7 −6.5893E−02 1.4911E−02 −4.1874E−038.7863E−05 3.9488E−05 7.0827E−05 0.0000E+00 8 −3.4127E−02 2.0251E−031.8783E−03 −1.2365E−03 2.2451E−04 3.2977E−05 −1.1683E−05

TABLE 5 Conic # R Thickness Material CA/2 coefficient K 0 Infinity1.00E+06 1 4.009 2.271 H-ZK3 2.96 0 2 18.115 1.547 2.55 0 3 −5.167 0.562EP6000L 2.00 −2.296 4 6.968 0.162 2.00 9.483 5 4.666 1.082 K26R 1.90−2.619 6 52.645 0.121 1.90 10.398 7 28.168 1.851 EP6000L 1.83 −367.355 8−5.062 0.101 1.83 −10.130 9 −5.098 0.291 K26R 1.76 −10.587 10 15.0004.115 1.76 −9.745 11 Infinity 0.210 BK7 2.44 12 Infinity 2.673 2.47 13Infinity 2.94

TABLE 6 # A1 A2 A3 A4 A5 A6 A7 1 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 37.1296E−03 −1.3791E−04 −2.8926E−05 3.7349E−06 0 0 0 4 −2.8741E−038.8769E−04 −1.2786E−04 2.0275E−05 0 0 0 5 −2.1504E−03 −3.1621E−04−3.2758E−06 −2.2831E−07 0 0 0 6 4.1139E−03 −1.9087E−03 1.9639E−04−3.2249E−05 0 0 0 7 −4.3880E−03 −7.7699E−04 1.8992E−04 −6.8854E−06 0 0 08 −6.5726E−03 −5.8651E−04 1.3315E−04 −2.0025E−05 0 0 0 9 −7.8205E−03−1.1425E−03 2.7014E−04 −4.0371E−05 0 0 0 10 −5.0642E−03 3.6557E−04−9.7321E−05 1.7319E−05 0 0 0

TABLE 7 Material Material refraction Abbe Conic # R Thickness indexnumber CA/2 coefficient K 1 2.271 1.127 1.67 54.96 1.8 7.979E−07 211.822 0.06 1.725 2.410 3 14.756 0.27 1.64 23.52 1.7 13.805 4 2.7280.974 1.45 2.902E−03 5 3.713 0.416 1.64 23.52 1.55 −2.868 6 3.524 0.7641.5 −8.486 7 −5.301 0.338 1.64 23.52 1.48 2.743 8 −4.321 0.212 1.6 2.5789 4.327 0.352 1.53 55.66 1.68 −9.755 10 3.771 2.656 1.8 −6.534 11Infinity 0.210 1.52 64.16 2.894 12 Infinity 0.401 2.938 13 Infinity —3.028

TABLE 8 # A1 A2 A3 A4 A5 A6 A7 1 4.421E−05 −2.009E−04 −1.152E−04−6.051E−10 2 6.027E−03 −1.244E−03 −5.380E−08 3 0.020 7.012E−04−1.081E−03 −6.297E−08 4 0.024 0.011 4.241E−04 −9.114E−08 5 −0.0228.939E−03 2.200E−03 −1.002E−06 6 −0.012 6.756E−03 −2.299E−03 1.314E−031.758E−04 −1.030E−05 7 −0.017 0.053 −0.044 7.968E−03 −1.599E−036.117E−04 7.436E−09 8 −0.086 0.159 −0.117 0.041 −9.090E−03 1.280E−032.793E−07 9 −0.252 0.182 −0.084 0.016 −6.759E−04 −1.940E−06 10 −0.1750.095 −0.040 8.597E−03 −7.751E−04 −8.160E−07

The examples provided with reference to FIGS. 2A and 2B illustrate acase where CA(S₁)=CH(S₁). In similar cases, CA(S₁) may be substantiallyequal to CH(S₁), for example with up to 5% difference.

In addition, an “aperture stop” 206 (which defines the lens aperture) islocated before the first surface S₁. The aperture stop can be e.g. amechanical piece. A lens module with an aperture stop located at orbefore the first surface S₁ is known in the art as a “front aperturelens”. Lens module 200 is a front aperture lens.

Note that in other examples, the stop may be located at a differentlocation or surface. In this case, this condition may not be true forthe first surface S₁. For example (this example being not limiting), theaperture stop can be located at the second surface S₂. In this case,CA(S₂)=CH(S₂). In similar cases CA(S₂), may be substantially equal toCH(S₂), for example with up to 5% difference.

According to some examples of the presently disclosed subject matter,there is provided an optical lens module comprising a plurality of lenselements where CH(S₁) of surface S₁ of lens element L₁ (closest to theobject side) is greater than CH(S_(k)) of each of all other surfacesS_(k) of the plurality of lens elements, with 2≤k≤2N.

For example, if N=4 (as in FIGS. 2A, 2B and 6), CH(S₁) is greater thanCH(S₂), CH(S₃), CH(S₄), CH(S₅), CH(S₆), CH(S₇) and CH(S₈). This appliesto different values of N.

For example, if N=4 (as in FIGS. 2A, 2B and 6), CH(S₂) is greater thanCH(S₃), CH(S₄), CH(S₅), CH(S₆), CH(S₇) and CH(S₈). This applies todifferent values of N.

For example, if N=5 (as in FIG. 20), CH(S₁) is greater than CH(S₂),CH(S₃), CH(S₄), CH(S₅), CH(S₆), CH(S₇), CH(S₈), CH(S₉) and CH(S₁₀). Thisapplies to different values of N.

For example, if N=5 (as in FIG. 20), CH(S₂) is greater than CH(S₃),CH(S₄), CH(S₅), CH(S₆), CH(S₇), CH(S₈), CH(S₉) and CH(S₁₀). This appliesto different values of N.

According to some examples, CH(S₁)≥X×CH(S₂), wherein X is any value inthe range [1.01;2] (such as X=1.1 or any other value in this range).

According to some examples, the following conditions are fulfilled:

-   -   CH(S₁)≥1.1×CH(S₂), and    -   CH(S₁)≥1.2×CH(S_(k)), for each of all other surfaces S_(k), with        3≤k≤2N.

According to some examples, the following conditions are fulfilled:

-   -   CH(S₁)≥1.45×CH(S_(k)), for each of all other surfaces S_(k),        with 3≤k≤2N.

According to some examples, the following condition is fulfilled:

-   -   CH(S₂)≥1.1×CH(S_(k)), for each of surfaces S_(k), with 3≤k≤2N.

According to some examples, the following conditions are fulfilled:

-   -   CH(S₁)≥X×CH(S₂), and    -   CH(S₁)≥Y×CH(S_(k)), for each of all other surfaces S_(k), with        3≤k≤2N, where Y>X. In some examples, X can be any value in the        range [1.01;2], and Y can be any value in the range [1.01;2].

According to some examples, the following conditions are fulfilled:

-   -   CH(S₂)≥Y×CH(S_(k)), for each of all other surfaces S_(k), with        3≤k≤2N, where Y>X. In some examples, Y can be any value in the        range [1.01;2].

According to some examples, CA(S₁) of surface S₁ of lens element L₁ isgreater than CA(S_(k)) of each of all other surfaces S_(k) of theplurality of lens elements, with 2≤k≤2N. According to some examples,CA(S₂) of surface S₂ of lens element L₁ is greater than CA(S_(k)) with3≤k≤2N.

For example, if N=4 (as in FIGS. 2A and 2B), CA(S₁) is greater thanCA(S₂), CA(S₃), CA(S₄), CA(S₅), CA(S₆), CA(S₇) and CA(S₈). This appliesto different values of N.

According to some examples, CA(S₁)≥X×CA(S₂), wherein X is any value inthe range [1.01;2] (such as X=1.1 or any other value in this range).

According to some examples, the following conditions are fulfilled:

-   -   CA(S₁)≥1.1×CA(S₂), and    -   CA(S₁)≥1.2×CA(S_(k)), for each of all other surfaces S_(k), with        3≤k≤2N.

According to some examples, the following conditions are fulfilled:

-   -   CA(S₁)≥1.45×CA(S_(k)), for each of all other surfaces S_(k),        with 3≤k≤2N.

According to some examples, the following condition is fulfilled:

-   -   CA(S₂)≥1.1×CA(S_(k)), for each of surfaces S_(k), with 3≤k≤2N.

According to some examples, the following conditions are fulfilled:

-   -   Y×CA(S₁)≥X×CA(S₂), and    -   CA(S₁)≥Y×CA(S_(k)), for each of all other surfaces S_(k), with        3≤k≤2N,        where Y>X. In some examples, X can be any value in the range        [1.01;2], and Y can be any value in the range [1.01;2].

According to some examples, CA(S₁) is substantially equal to CA(S_(2N))and is greater than CA(S_(k)) of each of all other surfaces S_(k) of theplurality of lens elements, with 2≤k≤2N−1. For example, if N=5 (as inFIGS. 21A and 21B), CA(S₁)=CA(S₁₀) is greater than CA(S₂), CA(S₃),CA(S₄), CA(S₅), CA(S₆), CA(S₇), CA(S₈) and CA(S₉). This applies todifferent values of N. In similar cases CA(S₁) may be substantiallyequal to CA(S₁₀), for example with up to 5% difference.

According to some examples, the following conditions are fulfilled:

-   -   CA(S₁)≥1.05×CA(S₂), and    -   CA(S₁)≥1.1×CA(S_(k)), for each of all other surfaces S_(k), with        3≤k≤2N−1.

According to some examples, the following condition is fulfilled:

BFL≥X×TTL,

In this equation, X is any value in the range [0.2;0.5]. According tosome examples, X=0.3 or X=0.4 where TTL and BFL are defined above.

In FIGS. 2A and 2B, the BFL is measured between the center of thesurface S₈ and the image sensor 202.

In FIGS. 2A and 2B, the TTL is measured between the center of thesurface S_(k) and the image sensor 202.

This configuration of the relative values of BFL and TTL as disclosedabove can improve the quality of the image formed on the image sensor.

Using a lens element L₁ with a front surface that has a greater CH valueor CA value with respect to the other surfaces can help to increase theamount of incoming light which can be sensed by the image sensor of thecamera or of the Tele sub-camera.

Advantageously, f/# (f-number) can be less than 3.

Advantageously, S₁ and\or S₂ can be spherical.

Advantageously, the ratio between the last lens element clear apertureCA(S_(2N)) and the sensor diagonal (SD) may be less than 0.8 or 0.7 or0.65.

Advantageously, TTL may be smaller than EFL.

According to some examples of the presently disclosed subject matter(tables 1-4), all lens elements L₁ to L_(N) may be made of plasticmaterial. According to some examples of the presently disclosed subjectmatter (Tables 5-6), lens element L₁ may be made of glass material andall lens elements L₂ to L_(N) may be made of plastic material. This ishowever non-limiting and lens elements L₁ to L_(N) may all be made byeither plastic or glass material. The selection of lens element material(plastic or glass) is influenced by various optical and mechanicaldemands For example, and as known in the art, different materials (glassand/or plastic) have different refractive indexes, glass havingtypically a higher refractive index selection range than plastic. Forexample, different materials have different Abbe numbers, glass havingtypically a higher Abbe number selection range than plastic. An examplefor 3 materials, refractive indexes and Abbe numbers is given above, outof hundreds of materials with corresponding Abbe numbers and refractiveindexes available. For example, the surface profiles of plastic lenselements may be approximated by a polynomial with many coefficients (4-7in the examples in Tables 1-6), while surface profiles of glass lenselements can be approximated in a similar way when molded or may belimited to spherical shape when polished (0 coefficient in the examplesin Tables 5-6). This limitation is driven from manufacturing limitsknown in the art. For example, the minimal thickness of a glass lenselement may be smaller than that of a plastic element, as known in theart. For example, glass lens elements may be cut (or diced or sliced) toa non-circular shape, as demonstrated in FIGS. 13A-13C.

In addition to the fact that at least the first lens element can be ofincreased dimensions in order to increase light impinging on the sensor,according to some examples, the barrel that holds the lens elements hasto be mechanically resilient to external stress while striving tomaintain the module height (along an axis perpendicular to the opticalaxis of barrel, which corresponds to axis Y in the figures) as low aspossible. This is advantageous for example when it is desired to fit acamera within the limited available space (e.g. thickness) of acomputerized device such as a Smartphone.

Examples of an optical lens module which is designed to deal with thesecontradictory requirements are described with reference to FIGS. 6-11,13, 17-19 and 22-25. The optical lens module is not limited to theexamples described with reference to FIGS. 6-11, 13, 17-19 and 22-25.

In the example illustrated in FIG. 6, barrel 64 of optical lens module60 comprises a cavity 61 surrounded by walls 62. In this example, afirst subset of the lens elements is held in cavity 61, and a secondsubset of the lens elements is located externally to barrel.

In particular, according to the example shown in FIG. 6, lens elementsL₂ to L_(N) are held within cavity 61 and lens element L₁ is locatedoutside of barrel 64 (that is to say that lens element L₁ is not withincavity 61). Lens element L₁ can be affixed to barrel 64, by anyappropriate mechanical link, such as an adhesive material.

In other examples, lens elements L₁ to L_(i) (with 1<i<N) are locatedoutside of barrel 64 (out of cavity 61), and lens elements L_(i) toL_(N) are held within cavity 61.

In the example of FIG. 6, since lens element L₁ is located outside ofcavity 61, the height H_(L1) of lens element L₁ can be substantiallyequal to or larger than the height H of barrel 64 (measured along theaxis Y between external surfaces of opposite walls of barrel 64).Heights H_(L2) to H_(LN) of lens element L₂ to L_(N) can be smaller thanthe height H of barrel 64. A numerical (non-limiting) example for lens60 may be have the following values: H_(L1)=4.82 mm,H_(L2)=H_(L3)=H_(L4)=3.7 mm.

Attention is now drawn to FIG. 7, which depicts another example of anoptical lens module 70.

In this example, optical lens module 70 comprises a barrel 74. Barrel 74comprises a cavity 71 circumvented by walls 72. According to the exampleillustrated in FIG. 7, lens elements L₁ to L_(N) can be all locatedwithin cavity 71.

According to some examples, a height H_(C) of cavity 71, measured alongan axis orthogonal to optical axis 103 (between internal parts 73), isvariable along optical axis 103.

In the representation of FIG. 7, height H_(C) of cavity 71 is measuredalong axis Y. For each position along the Z axis, height H_(C)corresponds in this example to the distance between the internal parts73 of walls 72 along axis Y. For cases in which the cavity barrel isaxial symmetric, H_(C) is the internal diameter of the cavity barrel. Inthe example of FIG. 7, cavity height H_(C) is variable along axis Z. Inother words, H_(C) (Z) is not a constant function.

According to some examples, cavity 71 comprises a first portion 76 inwhich first lens element L₁ is located and a second portion 77 in whichat least some of the other lens elements (L₂ to L_(N)) are located.

According to this example, height H_(C)(Z₁) of first portion 76 ofcavity 71 is greater than height H_(C)(Z₂) of second portion 77 ofcavity 71. As a consequence, first lens element L₁ (which is generallyof greater dimensions, as mentioned above) is positioned within firstportion 76 of cavity 71, and at least some of the other lens elementsare positioned within second portion 77 of cavity 71.

According to this example, height H_(C)(Z₁) of first portion 76 ofcavity 77 is designed to fit with the height H_(L1) of first lenselement L₁, and height H_(C)(Z2) of the second portion 77 of cavity 71is designed to fit with height H_(L2), H_(L3) and H_(L4) of the otherlens element L₂ to L₄ (in this example, H_(L2)=H_(L3)=H_(L4)).

The variable height of cavity 71 along optical axis 103 can be obtainede.g. by using walls 72 with a variable thickness. As shown in FIG. 7,walls 72 have a thinner thickness in first portion 76 than in secondportion 77. In other examples, walls 72 have a constant thickness butthey have a stepped shape.

Various examples (see FIGS. 8 to 13 and 17-19) of an optical lens modulecomprising a plurality of lens elements L₁ to L_(N) will now bedescribed. These optical lens modules can be used in any of the examplesof cameras or of optical designs described above. In these examples (seeFIGS. 8 to 13 and 17-19), the relationship between the dimensions of thelens elements can be in accordance with any of the examples describedabove (see e.g. FIGS. 2A to FIG. 5 and Tables 1-6) and are thus notdescribed again.

According to some examples, the height of lens element L₁ is greaterthan the height each of lens elements L₂ to L_(N) (in the examples ofFIGS. 8 to 13 and 17-19). Other relationships can be defined, as alreadyexplained above (these definitions can rely e.g. on a relationshipbetween the clear apertures and/or the clear heights of the lenselements).

Attention is now drawn to FIG. 8, which depicts an example of an opticallens module 80 comprising a plurality of lens elements L₁ to L_(N). Inthis example, four lens elements L₁ to L₄ are depicted. In this example,optical lens module 80 comprises a barrel 84. Barrel comprises a cavity81 circumvented by walls 82. At least some of lens elements L₂ to L_(N)are located within cavity 81.

The lens elements which are within cavity 81 have a center which issubstantially aligned with optical axis 103. The center of a lenselement can be defined as the physical center of the whole lens element(including the optical part and the mechanical part of the lens element,see e.g. in FIG. 11F wherein the physical center can be located at thecenter of the total height H_(L) of the lens element), or as the centerof only the optical portion of the lens element (see e.g. in FIG. 11Fwherein the optical center can be located at the center of the opticalheight H_(opt) of the lens element). Generally, the physical center ofthe lens element coincides with the center of the optical part (opticalcenter) of the lens element. For an axial symmetric lens element,H_(opt) is defined as the maximum of clear apertures of front and backsurfaces of the respective lens element.

In this example, extremity 83 of walls 82 is shaped so that extremity 83of walls 82 acts a stop for at least a portion of lens element L₁.

In particular, lens element L₁ is prevented from moving in the Y-Z planeby extremity 83 of the walls acting as a mechanical stop. By choosing anappropriate shape and appropriate dimensions for extremity 83 of thewalls 82, and likewise shaping a part of lens element L₁ to fit theshape of extremity 83, the center of lens element L₁ can besubstantially aligned with optical axis 103.

In the example of FIG. 8, the cross-section of extremity 83 of walls 82has a stepped shape.

An extremal portion 85 (this portion is part of the thickness of thelens element) of lens element L₁ is located within cavity 81. In someexamples, extremal portion 85 corresponds to the rear surface of lenselement L₁.

A main portion 86 (this portion is part of the thickness of the lenselement) of lens element L₁ is located outside of cavity 81. In someexamples, a thickness of extremal portion 85 measured along optical axis103 is less than a thickness of main portion 86 measured along opticalaxis 103. Extremal portion 85 of lens element L₁ is blocked betweenwalls 82. In particular, the stepped shape of extremity 83 of walls 82is made to match or to fit a part 87 of extremal portion 85 of lenselement L₁, wherein part 87 has also a stepped shape in cross-section.As apparent in FIG. 8, the stepped shape of extremity 83 fits togetherwith the stepped shape of part 87 of lens element L₁. Therefore, lenselement L₁ is prevented from moving in the Y-Z plane, and the center oflens element L₁ can be maintained in alignment with optical axis 103.

FIG. 9A describes another example of an optical lens module. In thisexample, the cross-section of extremity 93 of walls 92 has a slopedshape. In particular, extremity 93 can be shaped as a chamfer. Anextremal portion 95 (this portion is considered in the width of the lenselement) of lens element L₁ is located within a cavity 91 of barrel 94of optical lens module 90. In some examples, extremal portion 95corresponds to the rear surface of lens element L₁. A main portion 96(this portion is part of the thickness of the lens element) of lenselement L₁ is located outside of cavity 91. Extremal portion 95 of lenselement L₁ is prevented from moving in the Y-Z plane by extremity 93 ofwalls 92.

In particular, the sloping shape of extremity 93 of walls 92 is made tomatch or to fit a part 97 of extremal portion 95 of lens element L₁,wherein part 97 has also a sloping shape in cross-section. As apparentfrom FIG. 9A, the sloping shape of extremity 93 fits together with thesloping shape of part 97. Therefore, lens element L₁ is prevented frommoving in the Y-Z plane, and the center of lens element L₁ can bemaintained in alignment with optical axis 103.

FIG. 9B depicts a variant of FIG. 9A. In this example, a portion 98 oflens element L₁ is located within cavity. This portion 98 can correspondto a main portion of lens element L₁ or to the whole lens element L₁.Extremity 93 of walls 92 has a sloping shape in cross-section, as in theexample of FIG. 9A, but in this example the slope extends further alongthe side of lens element L₁. A part 97 of portion 98 is in contact withextremity 93 of walls 92, and has also a sloping shape in cross-section,which fits together with the sloping shape of extremity 93. Therefore,portion 98 of lens element L₁ is prevented from moving in the Y-Z plane.

FIG. 10 describes another example In this example, an extremal portion1005 (this portion is part of the width of the lens element) of lenselement L₁ is located within a cavity 1001, whereas a main portion 1006(this portion is part of the width of the lens element) of lens elementL₁ is located outside of cavity 1001. In some examples, extremal portion1005 corresponds to the rear surface of lens element L₁.

In some examples, a thickness of the extremal portion 1005 measuredalong optical axis 103 is less than a thickness of main portion 1006measured along optical axis 103.

Extremal portion 1005 of lens element L₁ is blocked between walls 1002.In particular, a part 1007 of extremal portion 1005 which is in contactwith an extremity 1003 of walls 1002 has a stepped shape. Extremity 1003of walls 1002 acts as a stop for extremal portion 1005, since part 1007is blocked by extremity 1003 and is prevented from moving in the Y-Zplane. Therefore, lens element L₁ is prevented from moving in the Y-Zplane, and the center of lens element L₁ can be maintained in alignmentwith optical axis 103.

In this example, the shape of walls 1002 can be uniform. In particular,the shape of extremity 1003 of walls 1002 can be identical with theshape of the other portions of walls 1002, contrary to the examplesdescribed in FIGS. 8, 9 and 9A, and only a part of the lens element isneeded to be shaped in order to fit extremity 1003.

According to some variants of the example of FIG. 10, a main portion oflens element L₁ is located within the cavity (and not only an extremalportion as in FIG. 10) and the extremity (see reference 1009 in FIG. 10)of the walls matches a part of lens element L₁ which has a steppedshape. Lens element L₁ is thus prevented from moving in the Y-Z plane.

Attention is now drawn to FIGS. 11A to 11E. According to some examples,an optical lens module 1100 can comprise lens elements L₁ to L_(N) and abarrel 1114. Barrel 1114 comprises a cavity 1101 surrounded by walls1102. N lens elements L₁ to L_(N) are located within cavity 1101. Inthis example, N is equal to four. The optical lens module can furthercomprise stops 1115, which can be present between each of two adjacentlens elements. Stops 1115 can have an annular shape. These stops 1115are useful for maintaining the lens elements at their required positionand for maintaining the required distance between the lens elements.

A height of barrel 1114, which can be measured, for example, betweenexternal surfaces 1103 of opposite walls 1104 of barrel 1114 (e.g. alongan axis Y orthogonal to a symmetry axis of barrel 1114) is equal to H.In the examples of FIGS. 11A to 11E, the height H_(L1) of lens elementL₁ can be substantially equal to H or greater than H. Thus, lens elementL₁ can have a large height (thus benefiting from an increased opticalcollection surface) while being located within the optical lens modulewhich provides protection and mechanical support of lens element L₁.With this configuration, the center of lens element L₁ can be maintainedin alignment with optical axis 103.

In addition, a lens element generally has an optical part and amechanical part. The mechanical part is the part of the lens elementwhich is not used for transmitting rays. This is visible for example inFIG. 11A, in which lens element L₂ comprises an optical part 1130 and amechanical part 1131. This is also illustrated in FIG. 11F.

According to some examples, the ratio between a height of the opticalpart (see H_(opt) in FIG. 11F) and the height of the lens element (seeH_(L) in FIG. 11F) is greater for lens element L₁ than for each of lenselements L₂ to L_(N).

As shown in the figures, barrel 1114 can comprise slots 1110 on two ofthe opposite walls 1111 of barrel 1114. This allows the lens element L₁to be substantially of the same height as the barrel, or to have aheight which is greater than the barrel, and to have a height which isgreater than that of the other lens elements. In particular, lenselement L₁ can be tangent to slots 1110, or at least part of the lenselement L₁ can protrude through slots 1110.

Attention is now drawn to FIG. 12 which describes an example of amanufacturing method of the optical lens module of FIGS. 11A to 11E. Themethod can comprise a step 1200 of providing a barrel comprising wallsdefining a cavity. The barrel can already comprise slots on at least twoopposite walls. Alternatively, the method can comprise creating slots inat least two opposite walls of the barrel.

The method can comprise a step 1201 of inserting lens elements L₁ toL_(N) in the cavity of the barrel. Generally, lens element L_(N), whichis the closest to the image side, is the first lens element to beinserted. Lens element L_(N) can be fastened to the barrel using afastening material such as an adhesive, so that it acts as a stop at oneside of cavity for the other lens elements.

According to some examples, stops are inserted within cavity, betweenthe lens elements, as already discussed with respect to FIG. 11A. Thelens elements are thus stacked within cavity. In order to prevent thelens elements from moving from their position, the method can comprise astep 1202 of fastening at least lens element L₁ in order to maintainlens elements L₁ to L_(N) within cavity. This can be performed byinjecting a fastening material (e.g. adhesive) within the cavity, e.g.through adapted through-holes 1120 present in the walls of the barrel.The adhesive thus fastens lens element L₁ to the internal surfaces ofthe walls. After these steps, and if necessary, the through holes canthen be plugged.

The structure of the lens module as depicted in FIGS. 11A to 11E is thusalso advantageous in terms of the manufacturing process, since lenselement L₁ can be of the height of barrel (or can have a height which isgreater than the height of the barrel) and can still be fastened to theinternal surfaces of the walls of the barrel (and not as in FIG. 6,where lens element L₁ is outside of the barrel and affixed only to anextremity of the walls of the barrel).

Attention is now drawn to FIG. 13A, which depicts an example of anoptical lens module 1380 comprising a plurality of lens elements 1381.Optical lens module 1380 comprises a barrel 1314. At least some of thelens elements can be located within barrel 1314.

According to some examples, at least part of the lens elements can havea shape (profile) in cross-section (in plane X-Y, which is orthogonal tothe optical lens module and which generally coincides with the opticalaxis) which is not circular. In particular, as shown e.g. in FIG. 13A,at least some of the lens elements can have a width W_(L) (measuredalong axis X) which is greater than their height H_(L) (measured alongaxis Y). The height H_(L) can correspond to the total height of the lenselement (including the mechanical part). In some embodiments, a lenselement in lens module 1380 may have a symmetry about axis Y and/orabout axis X.

According to some examples, W_(L) is substantially greater than H_(L)(for example, by at least a percentage which is equal or greater than10%, these values being not limiting).

According to some examples, at least part of the lens elements is shapedso as their profile in cross-section comprises sides with straightportions. Other sides of the profile can be e.g. curved. This can beseen e.g. in FIG. 13A, wherein sides 1350 (in this example two sides) ofthe profile of these lens elements in cross-section are substantiallystraight lines along axis X. As a consequence, at least some of thesides of these lens elements are flat surfaces (in plane X-Z). In FIG.13A, the two other sides 1351 of the profile of these lens elements incross-section are curved lines.

According to some examples, barrel 1314 is shaped to fit with the shapeof the lens elements. Thus, barrel 1314 can have walls which have aprofile in cross-section which is similar to the profile of the lenselements (located in barrel) in cross-section.

It is to be noted that other shapes and profiles can be used for thelens elements (and thus for barrel), such as (but not limited to) anelliptic profile.

The configuration described with reference to FIGS. 13A to 13C allows inparticular to increase the quantity of light received by the imagesensor, for a given height of barrel.

In the example depicted in FIG. 13B, lens element L₁, which is theclosest lens element to the object side, is located outside of barrel1314. Examples wherein lens element L₁ is positioned outside of barrelhave been described e.g. with reference to FIG. 6, and examples whereina main portion (measured along the thickness of the lens element) oflens element L₁ is located outside of barrel 1314 have been describedabove (see e.g. FIGS. 8 to 11E). At least part of the features describedwith reference to these examples can be used in the example of FIG. 13Band are not described again.

In the example depicted in FIG. 13C, lens element L₁, which is theclosest lens element to the object side, is also located within barrel1314. Examples wherein lens element L₁ is positioned within the barrelhave been described e.g. with reference to FIG. 7, and examples whereina main portion (measured along the thickness of the lens element) oflens element L₁ is located within the barrel have been described above(see e.g. the description of FIGS. 8, 9A and 10). At least part of thefeatures described with reference to these examples can be used in theexamples of FIG. 13A and FIG. 13C and are not described again.

Attention is now drawn to FIGS. 17A to 17D. FIG. 17A shows an isometricview of a lens module 1700. FIG. 17B shows a side view of lens module1700. FIG. 17C shows an exploded view of lens 1700. Lens module 1700 mayhave an optical design similar to lens 200. Lens module 1700 includes abarrel 1720. Lens module 1700 further includes lens elements L₁ toL_(N). N is normally in the range of 3-7, similar to lens module 200. Inthe non-limiting example of lens module 1700, N=4. Lens module 1700 hasthe first lens element L₁ partially positioned or placed outside ofbarrel 1720, while lens elements L₂ to L_(N) are placed completelyinside the barrel. L₁ is clearly seen in FIG. 17A, while other lenselements are not seen in this view but can be seen in FIG. 17B. Lensmodule 1700 has an optical axis 103 which serves as an axial symmetryaxis for all lens element L₁ to L_(N). Each lens element L_(i) has aheight H_(Li) defined along the Y axis. Lens element L₁ may have a“stepped” shape, i.e. it has a front part with height H_(L1) and a backpart with height H_(L1B), such that H_(L1)>H_(L1B). Lens module 1700 mayfurther include spacers R₁ to R_(N−1). Each spacer R_(i) is positionedbetween lens elements L_(i) and L_(i+1). In some embodiments, one ormore of spacers R₁ to R_(N−1) may be used as an aperture stop(s).

Barrel 1720 may be made for example from opaque plastic using plasticinjection molding, as known in the art. Barrel 1720 has a cavity 1740that may be axial-symmetric along optical axis 103. Cavity 1740 may havea shape of cylinder as in embodiment 1700 (FIG. 17B). In otherembodiments, cavity 1740 may have other axial symmetric shapes, such asa cone, a series of cylinders, etc. (see FIG. 17D). The axial symmetryaccuracy of cavity 1740 is important for the assembling accuracy, asknown in the art. In some embodiments, the tolerance for axial symmetrydistortion may be smaller than 10 μm, 5 μm or 1 μm.

Lens elements L_(i) may be made by plastic injection molding, as knownin the art. Lens elements L_(i) may be made from glass, as known in theart. Each lens element L_(i) has front surface (S_(2i−1)) and backsurface (S_(2i)) as defined above for embodiment 200. Each surface S_(k)(3≤k≤2N) may have an optically active part and a mechanical part whichis a non-active optical part (as described in FIG. 11F). A mechanicalpart may be used to handle the lens element during the molding andassembly stages. In some examples the mechanical part size may be on theorder of 100 μm-500 μm. For example, the mechanical part of S₁ is markedwith numeral 1751. The closest point of L₁ to the object side is markedwith numeral 1752.

FIG. 17D shows a lens module 1701 which is similar to lens module 1700with a single difference: barrel 2722 with cavity 1742 replaces barrel1720 with cavity 1740. Cavity 1742 has a shape of a series of cylindersin increasing sizes for each lens element; as can be seen in FIG. 17D,H_(L1B)≤H_(L2)≤H_(L3)≤H_(L4)<H_(L1). This feature may allow easiermolding of barrel 1720 and/or easier assembly of lens elements L₁ to L₄and spacers R₁ to R₃. In other embodiment the number of lens elementsmay differ from 4 as mentioned above. A numerical (non-limiting) examplefor lens module 1700 may be have the following values: H_(L1)=4.9 mm,H_(L1B)=3.65 mm, H_(L2)=3.7 mm, H_(L3)=3.8 mm, H_(L4)=3.9 mm

The assembly of lens module 1700 (or 1701) may be done in the followingsteps:

-   -   1. Insertion of lens element L₁ from the object side of barrel        1720. L₁ may be aligned to barrel 1720 due to the axial symmetry        of both elements.    -   2. Gluing of L₁ to barrel 1720. Gluing may be done using glue on        surface 1722, which is the front-most surface of barrel 1722.    -   3. Insertion of other elements from the image side of barrel in        the following order: R₁, L₂ . . . R_(N−1), L_(N). L₂ to L_(N)        and R₁ to R_(N−1) may be aligned to barrel 1720 due to the axial        symmetry of all elements.    -   4. Gluing lens element L_(N) to barrel 1720, for a non-limiting        example on surface 1724 which is the inner surface of barrel        1722.

Attention is now drawn to FIGS. 18A to 18C. FIG. 18A shows an isometricview of lens module 1800 which is similar to lens module 1700, exceptthat it has an added cover 1830. All other parts (barrel, lens elements,optical axis) are as in lens module 1700 and have the same numbering andnames. FIG. 18B shows a side cut of lens module 1800. FIG. 18C shows anexploded view of lens module 1800. Cover 1830 may be made from opaqueplastic, e.g. by plastic injection molding. Cover 1830 is positioned ontop of lens element L₁. In some embodiments, cover 1830 may opticallycover mechanical part 1751 such that cover 1830 prevents any optical rayof light arriving from the OPFE from reaching mechanical part 1751. Insome embodiments, cover 1830 may have a point 1831 which is closer tothe object than point 1752 on L₁. This feature is important in order toprotect lens module 1800 while handling and assembling, such that therisk of having lens element L₁ touching accidently another object isminimized.

The assembly process of lens module 1800 may be similar to the assemblyprocess of lens module 1700 above with an addition of a fifth step:

5. Positioning of cover 1830 and gluing it to barrel 1720 or to L₁. Inone example gluing may be done on surface 1724.

Attention is now drawn to FIGS. 19A and 19B, which show a lens module1900 similar to lens module 1800, except that a barrel 1920 replacesbarrel 1720. The change to barrel 1920 allows a different assemblyprocess (relative to lens module 1800), detailed below. FIG. 19A shows aside cut of lens 1900 and FIG. 19B shows lens module 1900 in an explodedview, according to the different assembly direction.

The assembly of lens module 1900 may be done in the following steps:

1. Insertion of lens element L_(N) from the object side of barrel 1820.

2. Insertion of other elements from the object side of barrel in thefollowing order: R_(N−1), L_(N−1), . . . R₁, L₁

3. Gluing lens element L₁ to barrel 1820 for a non-limiting example onsurface 1724.

4. Positioning of cover 1730 and gluing it to barrel 1820 or to L₁. Inone example gluing may be done on surface 1724.

The presently disclosed subject matter also contemplates a method offorming an image on an image sensor, using any of the examples describedabove.

The presently disclosed subject matter also contemplates a method ofproducing an optical lens module according to the specifications asdescribed by any of the examples above.

According to some examples, the digital camera can be integrated insidea housing of a mobile electronic device (such as, but not limited to, asmartphone, a portable computer, a watch, eyewear, etc.).

According to some examples, the optical lens module, associated with thelens elements, (as described in the various examples above), can beintegrated in a digital camera, or in a Tele sub-camera or in aplurality of Tele sub-cameras of a digital camera. This digital cameracan in addition comprise one or more Wide sub-cameras.

A folded camera can be used to reduce the height of elements of thecamera. As mentioned above, this can e.g. facilitate the integration ofthe camera when only limited space is available.

According to at least some of the examples described above, the proposedsolution can increase image quality by increasing the incoming lightthrough the camera aperture. This can be achieved notwithstanding anincrease of the distance (along Z axis) between the first lens element(at the object side) and the image sensor, as a result of a longer EFLused for obtaining an increased zoom factor.

In addition, according to at least some of the examples described above,the proposed solution can offer an optical lens module which can firmlyhold the lens elements while complying with the limited availableheight.

In addition, according to at least some of the examples described above,the quantity of light which is collected by the sensor is increased fora given height of barrel of the optical lens module.

As explained above, using a lens element L₁ incorporated in a lensmodule (the lens module comprising a plurality of lens elements, eachhaving a front surface and a read surface) with a front surface that hasa greater CH (clear height) value or greater CA (clear aperture) valuewith respect to the other surfaces helps to increase the incoming lightwhich enters the lenses barrel and can be sensed by an image sensor ofthe camera (e.g. Tele sub-camera in a dual aperture camera). As morelight can reach the sensor such configuration enables to increase thefocal length of the lens module.

It is known that a negative correlation exists between the focal lengthand a respective field of view, where the field of view becomes smalleras the focal length increases. Thus, while an increase to a given focallength in a given camera enables to increase image resolution, thehigher resolution image is formed on a smaller area of the camerasensor. In other words, when capturing an image of the same object fromthe same distance with two lenses, one having a focal length longer theother, the lens module with the longer focal length produces on thesensor a smaller image with higher spatial resolution as compared to theone with the shorter focal length. Thus, the advantages of a largerfocal length are accompanied with the disadvantage of a smaller sizeimage.

Accordingly, some examples of the presently disclosed subject matterinclude a digital camera as disclosed above comprising:

N lens elements L_(i) (lens module) having a symmetry along a firstoptical axis, each lens element comprising a respective front surfaceS_(2i−1) and a respective rear surface S_(2i), where i is between 1 andN, and N is equal to or greater than 3; wherein a clear height value ofsurface S₁ or a clear aperture value of surface S1 is greater than aclear height value or a clear aperture value of each of surfaces S₂ toS_(2N);

The digital camera further comprises an image sensor and a rotatingreflecting element or OPFB (such as a mirror or prism). The rotatingreflecting element is inclined with respect to the first optical axis,so as to provide a folded optical path between an object and the lenselements and is capable of being rotated around one or two axes.

An example of such rotating reflecting element is disclosed, by way ofexample in co-owned international patent application PCT/IB2017/052383,which describes an actuator of a digital camera designed to enable therotation of a reflecting element around two axes. See for example FIG.1A to FIG. 1F, FIG. 2 and FIG. 3 and the respective description inPCT/IB2017/052383 showing the design of an actuator which allows therotation of a prism around one or two axes.

Rotation of the reflecting element around one or two axes moves theposition of the camera FOV, wherein in each position a different portiona scene is captured in an image having the resolution of the digitalcamera. In this way a plurality of images of adjacent non-overlapping(or partially overlapping) camera FOV are captured and stitched togetherto form a stitched (also referred to as “composite”) image having anoverall image area of an FOV greater than digital camera FOV.

In some examples the digital camera can be a folded Tele cameraconfigured to provide a Tele image with a Tele image resolution, thefolded Tele camera comprising a Tele image sensor and its Tele lensassembly is characterized with a Tele field of view (FOV_(T)).

According to some examples, the folded Tele camera is integrated in amultiple aperture digital camera comprising at least one additionalupright Wide camera configured to provide a Wide image with a Wide imageresolution, being smaller than the Tele image resolution, the Widecamera comprising a Wide image sensor and a Wide lens module with a Widefield of view (FOV_(W)); wherein FOV_(T) is smaller than FOV_(W).Wherein rotation of the rotating reflecting element moves FOV_(T)relative to FOV_(W).

The description of co-owned international patent applicationsPCT/IB2016/056060 and PCT/IB2016/057366 includes a Tele camera with anadjustable Tele field of view. As described in PCT/IB2016/056060 andPCT/IB2016/057366, rotation of the reflecting element around one or twoaxes moves the position of Tele FOV (FOV_(T)) relative to the Wide FOV(FOV_(W)), wherein in each position a different portion a scene (withinFOV_(W)) is captured in a “Tele image” with higher resolution. Accordingto some examples, disclosed in PCT/IB2016/056060 and PCT/IB2016/057366,a plurality of Tele images of adjacent non-overlapping (or partiallyoverlapping) Tele FOVs are captured and stitched together to form astitched (also referred to as “composite”) Tele image having an overallimage area of an FOV greater than FOV_(T). According to some examples,the stitched Tele image is fused with the Wide image generated by theWide camera.

According to some examples, the digital camera further comprises or isotherwise operatively connected to a computer processing device, whichis configured to control the operation of the digital camera (e.g.camera CPU). The digital camera can comprise a controller operativelyconnected to the actuator of the rotating reflecting element andconfigured to control its operation for rotating the rotating reflectingelement.

The computer processing device can be responsive to a command requestingan image with a certain zoom factor and control the operation of thedigital camera for providing images having the requested zoom. Asmentioned in applications PCT/IB2016/056060 and PCT/IB2016/057366, insome examples a user interface (executed for example by the computerprocessing device) can be configured to allow input of user commandbeing indicative of a requested zoom factor. The computer processingdevice can be configured to process the command and provide appropriateinstructions to the digital camera for capturing images having therequested zoom.

In some cases, if the requested zoom factor is a value between theFOV_(W) and FOV_(T) the computer processing device can be configured tocause the actuator of the reflecting element to move the reflectingelement (by providing instruction to the controller of the actuator)such that a partial area of the scene corresponding to the requestedzoom factor is scanned and a plurality of partially overlapping ornon-overlapping Tele images, each having a Tele resolution and coveringa portion of the partial area, are captured. The computer processingdevice can be further configured to stitch the plurality of capturedimaged together in order to form a stitched image (composite image)having Tele resolution and an FOV greater than the FOV_(T) of thedigital camera. Optionally the stitched image can then be fused with theWide image.

FIG. 14 is a schematic illustration of an example of a stitched imagegenerated by capturing and stitching together 4 Tele images. In FIG. 14,1401 denotes FOV_(W), 1403 denotes FOV_(T) at the center of FOV_(W) and1405 indicates the size of the requested zoom factor. In the illustratedexample, four partially overlapping Tele-images (1407) are captured.

Notably, the overall area of the captured Tele-images (1407) is greaterthan the area of the requested zoom image (1405). The central part ofthe captured Tele-images is extracted (e.g. by the computer processingdevice as part of the generation of the stitched image) for generatingthe stitched image 1405. This helps to reduce the effect of imageartefacts resulting from transition from an image area covered by oneimage to an image area covered by a different image.

FIG. 15 is a schematic illustration of an example of a stitched imagegenerated by capturing and stitching together 6 Tele images. FIG. 16 isa schematic illustration of an example of a stitched image generated bycapturing and stitching together 9 Tele images. The same principlesdescribed with reference to FIG. 14 apply to FIGS. 15 and 16. Notably,the output image resulting from the stitching can have a different widthto height proportion than the single image proportion. For example, asillustrated in FIG. 15, a single image can have 3:4 proportion and theoutput stitched image can have a 9:16 proportion.

It is noted that image stitching per se is well known in the art andtherefore it is not explained further in detail.

FIG. 20 shows another exemplary embodiment of a lens module numbered2000 which includes N lens elements L_(i) (where “i” is an integerbetween 1 and N). In the example of FIG. 20, N is equal to 5. Forexample, L₁ is made of glass. The description above referring to lensmodule 200 holds also for lens module 2000, with the necessary change ofN from 4 to 5.

In some cases, both the first and last lens elements can be of increaseddimensions in order to increase light impinging on the sensor. Examplesof an optical lens module which is designed to deal with such a case isgiven in FIGS. 21-26.

FIG. 21A-B show another exemplary embodiment of a lens module numbered2100 which includes N lens elements L_(i). In the example of FIG. 21A-B,N is equal to 5. Lens module 2100 has the property of H_(L1)=H_(LN). InFIGS. 21A-B, lens module 2100 is shown without a lens barrel. FIG. 21Ashows light ray tracing of lens module 2100 while FIG. 21B shows onlythe lens elements for more clarity. In addition, both figures show imagesensor 202 and optical element 205.

FIG. 22 shows schematically in a side view an exemplary lens modulenumbered 2200 for holding the lens elements of lens module 2100. Lensmodule 2200 comprises a barrel 2202 having a cavity 2204 surrounded bywalls 2206. In lens module 2200, a first subset of the lens elements isheld inside the cavity, and a second subset of the lens elements islocated externally to (outside) the barrel. Specifically, lens elementsL₂ to L_(N−1) are held within cavity 2204 and lens elements L₁ and L_(N)are located outside of barrel 2202 (i.e. lens elements L₁ and L_(N) arenot within cavity 2204). Lens element L₁ and L_(N) can be affixed(fixedly attached) to barrel 2202 by any appropriate mechanical link,such as an adhesive material.

In lens module 2200, since lens elements L₁ and L_(N) are locatedoutside of cavity 2204, the height H_(L1) and H_(LN) of, respectively,lens elements L₁ and L_(N) can be substantially equal to the height ofbarrel 2202 (measured along the axis Y between external surfaces ofopposite walls of barrel 2202). Heights H_(L2) to H_(LN−1) of lenselement L₂ to L_(N−1) can be smaller than the height of barrel 2202,marked with H. A numerical (non-limiting) example for lens module 2200may be have the following values: H_(L1)=H_(L5)=4 mm,H_(L2)=H_(L3)=H_(M)=3.6 mm

FIG. 23 is a schematic representation of a side view of another opticallens module numbered 2300 for holding the lens elements of FIGS. 21A,21B. Lens module 2300 comprises a barrel 2302 having a cavity 2304surrounded by walls 2306. In lens module 2300, all the lens elements L₁and L_(N) are held (located) inside the cavity. Exemplarily, in lensmodule 2300, a height H_(C) of cavity 2304, measured along an axis Yorthogonal to optical axis 103, is variable along optical axis 103 (i.e.the Z axis). For each position along the Z axis, cavity height H_(C)corresponds in this example to the distance between the internal parts2308 of walls 2306 along axis Y. In other words, H_(C)(Z) is not aconstant function.

According to the example shown, cavity 2304 comprises a first portion2310 in which first lens element L₁ is located, a second portion 2312 inwhich the other lens elements (L₂ to L_(N−1)) are located and a thirdportion 2314 in which last lens element L_(N) is located. According tothis example, heights H_(C)(Z₁) of first portion 2310 and H_(C)(Z₃) ofthird portion 2314 are greater than height H(Z₂) of second (middle)portion 2312. As a consequence, first lens element L₁ and last lenselement L_(N) (which are generally of greater dimensions, as mentionedabove) are positioned respectively within first portion 2310 and thirdportion 2314 (respectively) of cavity 2304, and at least some of theother lens elements are positioned within second portion 2312 of cavity2304.

According to this example, height H_(C)(Z₁) of first portion 2310 isdesigned to fit with the height H_(L1) of first lens element L₁, heightH_(C)(Z₂) of second portion 2312 is designed to fit with height H_(L2),H_(L3) and H_(L4) of lens elements L₂ to L₄ (in this example,H_(L2)=H_(L3)=H_(L4)) and height H_(C)(Z₃) of third portion 2314 isdesigned to fit with the height H_(L5) of last lens element L₅.

The variable height of cavity 2304 along optical axis 103 can beobtained e.g. by using walls 2306 with a variable thickness. As shown inFIG. 23, walls 2306 have a thinner thickness in first portion 2310 andthird portion 2314 than in second portion 2312. In other examples, walls2306 may have a constant thickness but may have a stepped shape.

FIG. 24 is a schematic representation of a side view of anotherexemplary optical lens module numbered 2400 for holding the lenselements of FIGS. 21A, 21B. Lens module 2400 comprises a barrel 2402having a cavity 2404 surrounded by walls 2406. In this example, lenselements L₂ to L_(N−1) are located within cavity 2404. Lens elements L₁and L_(N) have a first part located inside cavity 2404 and a second partlocated outside of cavity 2404; this is similar to lens element L₁ ofFIG. 10A. An edge 2408 of lens element L₁ and an edge 2410 of lenselement L_(N) has a stepped shape. Walls 2406 align edges 2408 and 2410such that the center of lens elements L₁ and L_(N) can be maintained inalignment with optical axis 103.

Attention is now drawn to FIGS. 25A to 25D.

FIG. 25A is a schematic representation of an exploded isometric view ofanother exemplary optical lens module numbered 2500 having a lens barrel2502 and of a plurality of lens elements L₁ to L_(N) (in this exampleN=4) before their insertion into the barrel. FIG. 25B depicts across-section view of lens module 2500 along plane Y-Z, FIG. 25C depictsa cross-section view of lens module 2500 along plane X-Z, and FIG. 25Ddepicts another isometric view of lens module 2500 after the insertionof the lens elements into the barrel.

Barrel 2502 comprises a cavity 2504 surrounded by walls 2506. Lenselements L₁ to L_(N) are located within cavity 2504. Lens module 2500may further include spacers R₁ to R_(N−1). Each spacer R_(i) ispositioned between lens elements L_(i) and L_(i+1). In some embodiments,one or more of spacers R₁ to R_(N−1) may be used as an aperture stop(s).Spacers R₁ to R_(N−1) can have an annular shape.

A height H of barrel 2502 is measured for example between externalsurfaces of opposite walls 2512 of barrel 2502 (e.g. along an axis Yorthogonal to optical axis 103). In the examples of FIGS. 25A to 25D, aheight H_(L1) of lens element L₁ and a height H_(LN) of lens elementL_(N) can be substantially equal to H or greater than H. Thus, lenselements L₁ and L_(N) can have a large height (therefore benefiting froman increased optical collection surface) while being located within theoptical lens module which provides protection and mechanical support forlens elements L₁ and L_(N). With this configuration, the center of lenselements L₁ and L_(N) can be maintained in alignment with optical axis103.

Similar to FIGS. 11A-11F above, each lens element has an optical partand a mechanical part. According to some examples, the ratio between aheight of the optical part (see H_(opt) in FIG. 11F) and the height ofthe lens element (see H_(L) in FIG. 11F) is greater for lens elements L₁and L_(N) than for each of lens elements L₂ to L_(N−1).

As shown in the figures, barrel 2502 can comprise slots 2510 on the topand bottom wall of barrel 2502 on its two endings: close to the objectside and close to the image side. This allows lens elements L₁ and/orL_(N) to be substantially of the same height as the barrel, or to have aheight which is greater than the barrel height, and to have a heightwhich is greater than that of the other lens elements. In particular,lens elements L₁ and/or L_(N) can be tangent to slots 2510, or at leastparts of the lens elements L₁ and/or L_(N) can protrude through slots2510.

The structure of the lens as depicted in FIGS. 25A to 25D is thus alsoadvantageous in terms of the manufacturing process, since lens elementsL₁ and L_(N) can be of the height of the barrel (or can have a heightwhich is greater than the height of the barrel) and can still befastened to the internal surfaces of the walls of the barrel.

The assembly of lens module 2500 may be done using the following steps:

-   -   1. Insertion of lens element L_(N) from the image side of barrel        2502. L_(N) may be aligned to barrel 2502 due to the axial        symmetry of both elements.    -   2. Fixedly attaching (e.g. gluing) L₁ to barrel 2502.    -   3. Insertion of other elements from the object side of barrel        2502 in the following order: R_(N−1), L_(N−1) . . . R₂, L₁. L₁        to L_(N−1) and R₁ to R_(N−1) may be aligned to barrel 2502 due        to the axial symmetry of all elements.    -   4. Fixedly attaching (e.g. gluing) L_(N) to barrel 2502.

In one example, holes 2514 (FIG. 25D) in barrel 2502 may be used toinsert the glue to fasten lens elements L₁ and L_(N) in steps 2 and 4.

Attention is now drawn to FIGS. 26A to 26C. FIG. 26A shows an isometricview of another exemplary lens module numbered 2600. FIG. 26B shows aside view of lens module 2600. Lens module 2600 comprises a barrel 2602having a cavity 2604, and a plurality of lens elements L₁ to L_(N). N isnormally in the range of 3-7. In the non-limiting example of lens 2600,N=4. Lens module 2600 has the first lens elements L₁ and L_(N) partiallypositioned or placed outside of barrel 2602, while lens elements L₂ toL_(N−1) are placed completely inside the barrel. L₁ and L_(N) areclearly seen in FIG. 26A, while other lens elements are not seen in thisview but can be seen in FIG. 26B. As in previous examples, optical axis103 serves as an axial symmetry axis for all lens elements L₁ to L_(N).Each lens element L_(i) has a height H_(Li) defined along the Y axis.Lens elements L₁ and L_(N) may have a “stepped” shape, i.e. it has afront part with height H_(L1) (H_(LN)) and a back part with heightH_(L1B) (H_(LNB)), such that H_(L1)>H_(L1B) and H_(LN)>H_(LNB). Lensmodule 2600 may further include spacers R₁ to R_(N−1). Each spacer R_(i)is positioned between lens elements L_(i) and L_(i+1). In someembodiments, one or more of spacers R₁ to R_(N−1) may be used as anaperture stop(s). In some embodiments some adjacent lens elements maynot have a spacer therebetween.

Cavity 2604 may be made for example from opaque plastic and may be axialsymmetric along optical axis 103, like cavity 1720 in FIGS. 17A-17E. Inan exemplary embodiment, cavity 2604 may have a shape of cylinder as inembodiment 1700 (FIG. 17B). In other exemplary embodiments, cavity 2604may have other axial symmetric shapes, such as a cone, a series ofcylinders.

FIG. 26C shows a lens module 2601 which is similar to lens module 2600with a single difference: barrel 2622 with cavity 2624 replaces barrel2602 with cavity 2624. Cavity 2624 has a shape of a series of cylindersin increasing sizes for each lens element; as can be seen in FIG. 17D,H_(L1B)≤H_(L2)≤H_(L3)≤H_(L4)<H_(LNB)<H_(L1)=H_(LN). This feature mayallow easier molding of barrel 2620 and/or easier assembly of lenselements L₁ to L₄ and spacers R₁ to R₃. In other embodiments, the numberof lens elements may differ from four, as mentioned above.

The assembly of lens module 2400 (or 2401), and in particular the orderof lens element insertion into the barrel, may be similar to theassembly steps of lens module 1700 above (FIGS. 17A-17D).

Attention is now drawn to FIGS. 27. FIG. 27 shows an isometric view of alens module-2700 which is similar to lens module 2500, except that ithas an added cover 2730 similar to cover 1830 of lens 1800, with similarassembly steps.

Unless otherwise stated, the use of the expression “and/or” between thelast two members of a list of options for selection indicates that aselection of one or more of the listed options is appropriate and may bemade.

It should be understood that where the claims or specification refer to“a” or “an” element, such reference is not to be construed as therebeing only one of that element.

All patents and patent applications mentioned in this specification areherein incorporated in their entirety by reference into thespecification, to the same extent as if each individual patent or patentapplication was specifically and individually indicated to beincorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present disclosure.

What is claimed is:
 1. A digital camera, comprising: a) N lens elementshaving a symmetry along a first optical axis, wherein N is equal to orgreater than 3; b) an image sensor; c) an optical path folding element(OPFE) operative to provide a folded optical path from a first opticalpath to a second optical path; and d) a barrel with a cavity in whichthe plurality of lens elements are held, wherein a height of cavitymeasured along the first optical path is variable along the firstoptical axis, wherein the cavity comprises a first portion in which thefirst lens element L₁ is located and a second portion at which at leastone of the other lens elements is located, and wherein the height of thefirst portion of the cavity H₁ is greater than the height of the secondportion of the cavity H₂, so that H₁>1.1×H₂.
 2. The digital camera ofclaim 1, wherein the N lens elements have an axial symmetry.
 3. Thedigital camera of claim 1, wherein the digital camera has a total tracklength TTL and a focal back length BFL and wherein BFL≥0.3×TTL.
 4. Thedigital camera of claim 1, wherein lens element L₁ is made of glass. 5.The digital camera of claim 1, wherein lens element L₁ is made ofplastic.
 6. The digital camera of claim 1, wherein lens element L_(i) ismade of plastic for any 2≤i≤N.
 7. The digital camera of claim 1, whereinthe plurality of lens elements form a front aperture lens module.
 8. Thedigital camera of claim 1, wherein CA(S₁)<7 mm.
 9. The digital camera ofclaim 1, wherein CH(S₁)<7 mm.
 10. The digital camera of claim 1, whereinat least some of the lens elements have a width W_(L) greater than theirheight H_(L).
 11. The digital camera of claim 1, wherein a height ofcavity, measured along an axis orthogonal to the first optical axis, isvariable along the first optical axis.
 12. The digital camera of claim1, wherein lens element L₁ has a portion that is not completelysurrounded by the cavity and wherein walls of the cavity align a centerof lens element L₁ with the first optical axis.
 13. The digital cameraof claim 10, wherein lens element L_(N) is located outside the barrel.14. The digital camera of claim 12, wherein lens element L_(N) has aportion that is not completely surrounded by the cavity and whereinwalls of the cavity align a center of lens element L_(N) with the firstoptical axis.
 15. The digital camera of claim 12, wherein at least oneof an extremity of the walls and an extremity of lens element L₁ isshaped so that the extremity of the walls acts a stop for at least aportion of lens element L₁, thereby aligning a center of lens element L₁with the first optical axis.
 16. The digital camera of claim 14, whereina first portion of lens element L₁ is located in the cavity between theextremity of the walls and a second portion of lens element L₁ islocated outside the barrel and wherein a thickness of the second portionof lens element L₁ long the first optical axis is greater than athickness of the first portion of lens element L₁ along the firstoptical axis.
 17. The digital camera of claim 14, wherein across-section of the extremity of the walls has a stepped shape.
 18. Thedigital camera of claim 14, wherein a cross-section of the extremity oflens element L₁ has a stepped shape.
 19. The digital camera of claim 14,wherein a cross-section of the extremity of the walls has a slopingshape.
 20. The digital camera of claim 14, wherein the extremity of thewalls comprises a chamfer.
 21. The digital camera of claim 12, furthercomprising a cover for covering and protecting lens element L₁.
 22. Thedigital camera of claim 21, wherein the cover has an extreme pointbeyond lens element L₁.
 23. The digital camera of claim 21, wherein thecover blocks light from entering a mechanical part of lens element L₁.